He was quizzed in connection with the alleged Chinese plot after his arrest in an “ultra-discreet” swoop by officers from Scotland Yard’s SO15 counter-terrorism command at his home on Tuesday - but released on bail hours later.

Mr Jones, who describes himself as a “visiting professor” in “gas turbine combustion” at the Aeronautical Uni­versity of Xian, central China, was held on suspicion of brea­ching the Official Secrets Act.

Section One of the Act, rel­ating to national security, ca­rries a maximum 14 years’ jail.

Last night a source said: “China and Russia are determined to steal state ­se­crets by any means. Any arrest of this type is highly significant.”